Such exhaust gas feed devices have previously been described in a number of applications. The purpose of these feed devices is to provide a good mixing of the exhaust gas flow with the air flow. It must be provided, however, that a sufficient pressure gradient be maintained in the exhaust gas recirculation duct so that sufficiently large quantities of exhaust gas can be recirculated. Significant pressure losses must therefore be avoided.
Besides feed devices which are formed by a slotted duct wall, for example, through which exhaust gas can flow radially from a surrounding ring duct into the air intake duct, as described, for example, in DE 44 20 247 A1, static mixers have also been described which provide for sufficient mixing after exhaust gas has been fed into the air flow. A plate-shaped static mixer is described, for example, in DE 10 2004 025 184 A1.
Another static mixer is described in U.S. Pat. No. 7,743,756 B2. This mixer has an inner exhaust gas recirculation duct with radial outflow openings behind which swirl-generating vanes are formed through which the mixed exhaust gas airflow passes so that turbulence is caused which is intended to result in a homogenization of the mixture immediately in front of the throttle.
With such a mixing by means of static mixers, previously existing strands of a gas in the gas mixture might be deflected in the same manner as the surrounding gas so that a satisfactory mixing is still not achieved. Mixing by means of a radial feed provides for a relatively good mixing while, however, resulting in a high pressure loss.
The quantity regulation for the fed exhaust gas flow is also located at a distance from the feed location so that pulsations and pressure differences in the downstream exhaust gas system make an accurate regulation difficult.